Gas turbine with throttling air turbine in compressor intake



Aug. 21, 1951 J. L. RAY 2,565,324

GAS TURBINE WITH THROTTLING AIR TURBINE IN COMPRESSOR INTAKE} Filed Sept. 16, 1946 4 Sheets-Sheet 1 INVENTOR. .JMJ.L.FAY.

Aug. 21, 1951 Filed Sept. 16, 1946 J. L. RAY GAS TURBINE WITH THROTTLING AIR TURBINE IN COMPRESSOR INTAKE 4 Sheets-Sheet 2 ATZWF/VEY Aug. 21, 1951 J. RAY 2,565,324

GAS TURBINE WITH THROTTLING AIR TURBINE IN COMPRESSOR INTAKE Filed Sept. 16, 1946 4 Sheets-Sheet 5 I ENTOR.Y 6 MHL.FAK

ATTORNEY Patented Aug. 21, 1951 GAS TURBI Nl'sl wrrn THROTTLING AIR TURBINE IN COMPRESSOR INTAKE James L. Ray, Long Beach, Calif., assignor, by

mesne assignments, to General Electric Company, Schenectady, N. Y., a corporation of New York Application September 16,1946, Serial No. 697,272

3 Claims. (01. (iii-39.2)

The present invention relates to gas turbine power plants of the type employing a combustion gas turbine having an associated air compressor for supplying air under pressure to a fuel combustion chamber and more particularly to an improved means for maintaining an improved overall efllciency in the unit when operating at widely varying altitudes and loads.

An object of the invention is to provide a throttling means for controlling the flow of air to the compressor of a gas turbine unit in which the loss in efilciency due to the throttling means can be recovered as useful work.

Another object of the invention is to provide an improvement in gas turbine units of the type employing an air compressor in which an auxiliary turbine is used as a throttling means to control the mass flow of air to the intake of the compressor.

Another object of the invention is to provide a new and novel throttling arrangement for gas turbines of the type employing an air compressor in which any loss in the over-all eiliclency of the gas turbine unit due to the throttling means may be in part recovered as useful work.

Another object of the invention is to provide in combination with a throttling means a heat recovery means that will take advantage of the increased temperature difference, due to the higher exhaust temperature and lower compression temperature, resulting from the reduced mass flow at partial loads and thereby also obtain a' high rate of heat recovery.

The foregoing and other objects of the invention, which will be apparent to those skilled in the art, are attained by means of a novel combination and arrangement of parts to be hereinafter described and claimed, and in order that the same may be better understood, reference is had to the accompanying drawings which illustrate the now preferred form of the invention. It is to be understood, however, that the inventive conception is capable of many other mechanical expressions within the scope of the subject matter claimed hereinafter.

In the drawings: 7

Figure l is a side elevation in outline showing a combustion gas turbine unit of a type suitable for the utilization of my invention,

Figures 2 and 3 are, respectively, a plan and an end view of the gas turbine unit shown in Figure l of the drawings,

Figure 4 is an enlarged fragmentary sectional view taken in a vertical plane through Figure 1 or on line 4-4 of Figure 8. oi the drewingl,

Figure 5 is a fragmentary view showing details of the invention as illustrated in Figure 4 of the drawings,

Figure 6 is a view similar to Figure 5 showing a modified form of the invention,

Figure 7 is a fragmentary sectional view showing a further modified form which the invention may take,

Figure 8 is an enlarged sectional view of a porltion of the arrangement shown in Figure 7, an

Figure 9 is a diagrammatic curve showing the operating characteristics of the invention under different conditions of operation.

In the design of combustion gas turbine units for aircraft and like usages where the unit may be operated at widely different altitudes, it is generally the practice to design'the gas turbine for normal operation at the highest altitude at which operation will be required. However, with such a design, when the gas turbine unit is operated at a low altitude it will deliver for more than its rated power output. Therefore in order to reduce the output of such a turbine unit so that its output will not exceed the capacity of a propeller, an electric power generator or other driven device connected thereto, it has been found necessary to provide a means whereby the temperature of the combustion gases delivered to the gas turbine can be reduced. It is known that a gas turbine unit designed for high altitude operation at its rated temperature may be also operated at sea level and at its normal rating by simply restricting the mass flow of air to the compressor intake.

pressor, a considerable loss in efliciency occurs due to the resulting increase in entropy. To reduce this loss in efliciency I propose by my present invention to interpose an air turbine in the intake duct of the compressor through which the air flow to the compressor ..will pass and thus develop' a certain amount of power and in order to recover this power I also mount the rotor of this air turbine unit upon the main shaft of the gas turbine unit so that it will return useful work to the unit. While this is the preferred arrangement it will be understood that the .throttling air turbine may be operated entirely separate from the air compressor and the work recovered b it may be utilized in some other way; for example, it may operate to drive an electric generator, the power output of which will be credited to the output of the gas turbine. In this manner, by properly proportioning the flow areal throulb V However, when this isdone by a simple throttling of the air flow to the com-.

this air turbine, the mass flow of air to the compressor can be reduced to the desired quantity which will enable the gas turbine unit to operate at its rated high altitude inlet temperature and with a maximum possible efllciency when operat ing at low altitudes V In order to apply a throttling means, such as is contemplated by my present invention, to a gas turbine designed as suggested above for operation at high altitudes, I mount the throttling air turbine rotor element within an air flow directing cowling at the intake end of the compressor and in this cowling I provide a by-pass conduit through which the inflowing air may flow in by-passing relation to the air throttling air turbine rotor element and directly to the air compressor intake. Associated with this bypass conduit I also provide a valve member or air flow controlling means that can be operated to completely or partially close the by-pass conduit when the turbine unit is operating at a low altitude and thus all of the air entering the compressor will be caused to flow through the throttling air turbine, with the result that the flow of air to the compressor will be throttled and reduced in mass.

In other words, when the gas turbine unit is equipped with such a throttling means, as above described, and is in operation at the altitude for which it is designed the turbo-compressor of the gas turbine unit will take its incoming air directly from the air flow directing cowling in by-passing relation to the throttling turbine, and when operating at sea level, or at a low altitude, the by-passing conduit will be closed so that the incoming flow of air to the compressor will be caused to flow through the throttling turbine rotor element and thus the mass flow of air to the turbine may be controlled to provide any desired degree of regulation. At the same time, when the gas turbine is operating with the throttling turbine rotor element in operation, the throttled air passing through the throttling turbine will give up energy which will be in turn applied to the main shaft of the gas turbine unit and, as a result, it will be seen that any loss in efllciency resulting from the throttling of the mass flow of air to the compressor in this manner will be, at least in part, compensated for by the energy that will be developed by the operation of the throttling turbine.

From the above, it will be understood that the function of the throttling turbine, as here proposed, is to restrict the mass flow of air to the turbo-compressor in accordance with the output desired from the gas turbine unit and, at the same time, to recover as much as possible of the energy made available by the operation of the throttling turbine. Then by properly proportioning the flow areas of the throttling turbine, the mass flow of air to the compressor can be reduced to any desired quantity that will enable the gas turbine unit to operate at its rated inlet .temperature and thus at its maximum possible efliciency under low altitude conditions. It will also be readily understood that the principle here involved may be utilized to improve the partial load economy and the thermal efficiency of a gas turbine unit that may be designed for full load operation at any definite altitude, as the interposed throttling turbine may then be used to reduce the mass flow of air to the compressor in a manner that will result in an increased gas temperature at the gas turbine inlet when the gas turbine unit is operating under a partial ioad at this same altitude;

For a general understanding of the application of the invention to a combustion gas turbine unit of the type contemplated by my invention, reference is now made to Figures 1,- 2 and 3 of the drawings wherein my improved compressor throttling means, designated broadly by the numeral I0, is shown as disposed at the intake end of an axial flow turbo-compressor unit II which has its intake end disposed closely adjacent a driv= ing gas turbine unit I2 and with its discharge end l3 connected by conduits l4 and I5 to heat exchange units of conventional form that are disposed respectively in turbine exhaust manifolds l6 and ll of the main gas turbine unit 12. After passing through the heat exchange units in the exhaust manifolds l6 and l! the compressed air is discharged into two combustion chambers I8 and I9 that are disposed horizontally at opposite sides of the axis of the turbine unit l2. These combustion chambers I8 and I9 have fuel injecting nozzles 20 and 2 I, and are adapted to in turn discharge hot gases into an annular manifold 22 that communicates directly with the interior of the gas turbine I2. In this particular assembly the rotors of the air compressor II and the gas turbine l2 are connected for rotation as a unit and at the discharge end of the compressor unit II the main shaft of the unit is extended for connection to any suitable load. As here shown the shaft extension is connected directly to an electric current generator 23. As accessories the shaft of the unit is also adapted to drive a tachometer 24, a fuel pump 25, and a load responsive governor 26, all of which are here shown as mounted upon the exterior of a gear drive enclosing housing 21 that also serves as a support for a starting motor 28 by which the unit may be initially set in operation. A lubricating oil tank 29 with an immersed oil pump is also here shown as mounted upon the gear drive enclosing housing. In connection with these figures of the drawings it will be noted that the assembly here shown is of special construction in that the gas turbine, the air compressor and the other elements of the unit are supported in cooperating relation with each other by a structural framework in which longitudinally extending tie-bars 30 are employed to secure the several elements of the unit in cooperating relation. However, it is to be understood that the present invention may be applied to any form of gas turbine unit employing a gas turbine and air compressor. In this particular unit, for convenience in arranging the air connections, the intake end of the compressor II is arranged closely adjacent the gas turbine l2 and between the compressed air conduits l4 and Hi. It will also be noted that at the compressor end of the assembly the framework is provided with two foundation engaging pads 3| which, in conjunction with a single foundation engaging pad 32 at the other end of the unit, provide a three-point mounting for the entire assembly.

Upon now referring to Figure 4 of the drawings it will be seen that the gas turbine unit l2 has a rotor member 33 that is direct connected through a flanged coupling 34 to a rotor member 35 which forms a part of the air compressor unit ll. These rotor members 33 and 35 of the gas turbine l2 and the air compressor l l are rotatably mounted in an end bearing 36 at the outer end of the gas turbine unit I2, a second bearing 31 that is located between the rotor members 33 and 35 and a third bearing (not shown) that is the intake of the compressor unit located at the outer end 01 the air compressor unit The gas turbine II as here shown has a housing 38 which communicates with the interior of the annular manifold 22 of the combustion gas turbine unit l2 and at this point of Juneture the housing 33 is provided with radially spaced'nozzle forming blades or partitions 33 that serve to direct; the fiow of hot gases into a series of rotary buckets or blades 40 that are carried by the rotor member 33 and which form the first stage of the gas turbine l2. The housing 38 also carries two further sets of radially disposed buckets or nozzle forming blades 4| and 42 with which rotary buckets or blades 43 and 44 carried by the rotor member 33 cooperate to form a second and third stage of expansion within the gas turbine l2. After passing through these gas directing nozzles and over the buckets or blades between the rotor member 33 and the housing 33 the hot gases will be discharged into the exhaust manifolds l6 and I1, previously referred to in connection with Figures 1, 2 and 3 of the drawings. In order to confine the flow of the hot combustion gases and prevent leakage at the ends otthe rotor member 33 there is a labyrinth type gas seal 45 at one end of the rotor member 33 and at its other end there is a similar gas seal 46. In this arrangement it will be noted that the rotor member 35 of the air compressor unit II is in the form of a hollow cylinder and it has a flanged extension 41 that connects with the coupling 34 at the other side of the bearing 31. An enclosing housing 43 is also here shown as disposed about the rotor member 35 and extending from the outer surface of the rotor member 35 there is a plurality of annularly arranged sets of blades or buckets 43 that cooperate with the interposed and correspondingly spaced sets of nozzle forming or intermediate stationary blades 50 that extend inwardly from a housing 48 of the air compressor unit II. In thismanner there is formed multiplicity of axial fiow air compressing stages throughout the length of the compressor unit II. The rotor member 35 of the air compressor unit H is also here shown as somewhat displaced axially from the end oi the rotor member 33 of the gas turbine I2 by the interposition of the intermediate supporting bearing 31. Thi spacing between the rotor members 33 and 35 of the unit permits a location of the intake end of the air compressor adjacent the exhaust manifolds l6 and H of the gas turbine l2. At this point and extending around the bearing 31 and in communication with the intake end of the air compressor unit N there is a housing or shroudlike cowling 5| thathas a screened or perforated annularwall 52 through which air may flow to This housing or shroud-like cowling 5| bows outwardly from the intake end of the compressor unit II and disposed therein is a stationary annular extension 53 that has spaced annular rows of bypass ports 54 and 55 that extend radially therethrough and through which, as will hereinafter appear, incoming air may flow directly to the intake of the air compressor unit At the outer end of this extension 53 and beyond'the by-pass ports 54 and 55 there is a series of spaced radially extending air flow directing nozzle forming partitions 56 between which air may also flow from the interior of the cowling 5| to the intake of the air compressor l I. These air flow directing partitions 56 are supported at their inner ends by a stationary bearing housing 51 in which the bearing 31 is mounted. Associated with these nozzle forming partitions 56 there is a bladed turbine rotor element 58 that is carried by an annular extension 53 which is secured to the flanged extension 41 of the air compressor rotor member 35 by means of bolts 33. It will be here noted that the outer end of the extension 53 is of streamline configuration and that the ports 54 and 55 formed therein are so shaped as to permit of a free flow of air to an annular series of spaced nozzle forming partitions 6| at the inlet of the compressor which serve to direct the incoming air into the first set of blades or buckets 43 upon the rotor member 35. Movably associated with the stationary extension 53 there is also a cylindrical sleeve or valve member 62 that is adapted to be moved axially so as to cover and uncover the ports 54 and 55 therethrough.

As is more clearly shown in Figure 5 of the drawings, the extension 53 through which the ports 54 and 55 extend is provided with spaced axially extending webs 63 that serve to form an integral unit and define the sides of the ports 54 and 55. These webs 63 are extended at one end as at '64 so as to support the free end of the cylindrical valve member 62 and at their other ends these webs 63 extend outwardly over the housing 48 of the air compressor unit II as at 65 to provide a further support and guides over which the cylindrical valve member 62 may freely slide when it is moved into and out of the enclosing housing or cowling 5|. It will be noted that the cylindrical valve member 63 is adapted to extend beyond the ports 54 and 55 of the extension 53 in such a manner that when in its extreme inner position it will also serve to throttle ing 5| to uncover the ports 54 and 55 of the ex-' tension 53 it Will be held in this position by the extensions 65 previously referred to as disposed outwardly and over the housing 58 of the air compressor unit As a means for operating the cylindrical valve member 62 between its limits of movement, as above suggested, there is a plurality of spaced tie-bars or operating rods 66 that extend outwardly, and as shown in Figures 1 and 2 of the drawings, these tie-bars or operating rods connect with a ring or yoke-like member 61 that is adapted to be moved by one or more piston rods 63 that operate from hydraulic cylinders or servomotors 69 which are in turn controlled in any well known manner by the load responsive governor 26. While it is conceivable that the operation of the tie-rods 66 may be controlled manually or by other mechanical means, in this instance the load responsive governor 25 operates through a valve means 10 to control the flow of fluid to one or the other end of the cylinder 63 as the speed of the gas turbine unit changes, due to load and/or other variables such, for example, as a change in the altitude at which the unit is operatmg.

To increase the range over which the throttling turbine will operate efliciently, it may be desirable to make the nozzle vanes movable so that the area can be changed by the governor to suit the mass flow requirements of the gas turbine, as shown in Figures 7 and 8. Here the vanes 56 are mounted on axles 56a, each carrying at one end thereof a gear 56b. All gears 56!) mesh with a ring gear 56c, which is rotated by a pinion 56d driven by a shaft 560 from outside how sing 5|. The area of the-nozzle passages can then be adjusted to suit the air flow required, and this action can be used to supplement the action of sleeve valve 62. If desired, shaft We can be governor operated.

Since is is conceivable that there may be conditions of operation under which it will be found desirable to control the degree of throttling that may result from an installation of the throttling turbine as above described, there is shown in Figure 6 of the drawings an arrangement, by which this may be accomplished. In this particular modification of the invention the throttling turbine rotor element, here designated by the numeral II, is provided with a series of spaced radiall extending blades 12 that have concentrically arranged partitions l3 and 14 which, as will be understood, will serve to divide the blades 12 into three distinct working zones. In association with these turbine blades 12 there is also provided a series of radially extending nozzle forming blades or partitions 15 at the outlet end of the cowling 5|, that are divided by concentrically arranged partitions l6 and 11 which serve to form three concentrically arranged se.s of nozzles. Associated respectively with each of these concentrically located partitions l6 and 11 there are annular curved baffles l8 and 19. These curved bailles l8 and I9 follow the general contour of the cowling 5| and the streamlined end of the extension 53 and in this way there are formed three annular passageways wi.hin thecowling 5|, each one of which will serve to direct the incoming air from the cowling 5| to one or more of the working zones of the blades 12. To control the flow of air through these three pasageways the valve member 62, previously described, is arranged to extend into the cowling 5| and over the ou-er edges of the annular curved baflies l8 and 19 so that when it is moved axially by the tie-bars or operating rod 66 in the manner above described one or more of the air directing pasageways between the end of the extension 53 and the inner wall of the cowling 5| may be opened to permit the flow of incoming air to one or more of the working zones of the throttling turbine blades l2. In this way the throttling efiect of the turbine rotor blades 12 upon the flow of air to the intake of the compressor unit ma be regulated to provide any degree of throttling desired, and thus maintain the'necessary mass flow of air to the compressor unit H and at the same time much of the loss in over-all efficiency which may result from the increased entropy of the air now throttling turbine will be returned to the driving shaft of the gas turbine unit.

It is believed that the opera .ion of my invention will be clearly understood from the above description by those skilled in the art. Referring to Figure 9, which is a temperature-entropy diagram of a throttled and non-throttled cycle, it will be seen that in 'the throttled cycle there is a much larger temperature difference as compared to the temperature difierence C-D for the non-thro tied cycle. Theoretical calculations as well as experience indicates that a given amount of heat exchanger surface will recover approximately the same percentage of the heat represented by these temperature differences in both cases. Therefore, the greater the temperature difference the larger the heat recovery from the exhaust and the less fuel required to raise the air temperature to the operating value. This heat recovery means may be in the form of a heat exchanger, by means of which the gas tur- 8 bine exhaust is caused to heat the compressed air discharged from the compressor before it enters the combustion chamber. It may be added that in the case of a unit such as is here described there will be provided temperature responsive control means of conventional design for controlling the fuel input to the gas turbine and thus maintain a constant normal working temperature at the gas turbine inlet. With such an arrangement the constant speed governor 26 will operate to adjust the position of the cylindrical valve member 62 within the cowling II and thereby regulate the flow of air to the intake of the compressor unit H) to correspond with the load imposed on the gas turbine I2 by the generator 23. For example, if it is assumed that the unit, as shown, is operating at a partial load, any increase in the generator load will produce a small drop in the speed of the unit. This will cause the governor 26 to act through its control valve 10 and the hydraulic cylinder or servo-motor 69 and cause the valve member 62 to move in a direction that will admit a greater flow of air to the intake of air compressor II. This greater flow of air will then produce a slight drop in temperature at the inlet of the gas turbine l2 and this will cause the fuel regulating temperature responsive device to increase the flow of fuel to the combus- 30 tion chambers l8 and i9 and thus increase the heat energy input to the turbine by an amount comparable with the increase in the load. From this it will be obvious that other control arrangements can be devised to suit any conditions under which the unit equipped with a throttling means of the type above described may be required to operate.

When the air compressor II and the gas turbine l2 are so proportioned that the correct amount of air will be passed through the unit to deliver the rated power output, with a definite turbine inlet temperature, and the unit may be required to operate at widely varying altitudes and low ambient temperatures, as for example, at 40,000 ft. elevation and at 67 F., and occasionally at lower altitudes and higher ambient temperatures, say at sea level and at a temperature of 60 F., the throttling turbine will also be proportioned so as to pass a throttled quantity of air such that, after passing through the compressor H, the heat exchange means in the exhaust manifolds l6 and I1, and the combustion chambers Hi and I9, where it will be heated to the maximum allowable operating temperature and thence to the gas turbine l2, the rated power output of the turbine unit will be de-' veloped. With a unit of this type operating at its higher altitude the by-pass valve 82 at the intake end of the compressor U will be nearly or completely open so that all or most of the incoming air will flow to the inlet of the compressor unit directly through the ports 54 and 55 with very little or none of the air passing through the blades 58 of the throttling turbine.

; Under these conditions of operation the rotational losses of the throttling turbine will be negligible due to the low density of the air at higher altitudes. In like manner, when such a turbine unit is operating at sea level the bypass ports controlling valve member 62 will be moved in such a manner as to nearly or completely close the by-pass ports 54 and 55 and as a result the air which will flow from the cowling 5| to the inlet of the compressor unit II will be caused to flow almost entirely or entirely through the air directing nozzles 56 and the turbine blades 58. This will cause the pressure at the inlet of the compressor H to become more or less depressed due to the air restricting effect of the throttling turbine. However, as pointed out above, the advantage of this arrangement over a simple valve type throttling arrangement resides in the fact that the air flowing through the throttling turbine will produce mechanical energy that will be available as an additional force to drive the compressor unit H.

It will be understood that the invention is not to be construed as limited to the specific forms and arrangements herein disclosed but may be embodied in other forms and arrangements that will suggest themselves to persons skilled in the art. It is believed that this invention is new and it is desired to claim it so that all such modifications as some within the scope of the appended claims are to be considered as part of this invention.

Iclaim:

i. In a throttling arrangement for an open cycle combustion single main gas turbine unit of the type employing a directly connected rotary compressor, the combination of an air compressor housing having an intake and a discharge end, a rotor element mounted within said housing and adapted when in rotation to deliver compressed air at the discharge end of said housing in the total amount required for combustion and expansion in said turbine, an extension at the intake end of said air compressor housing having radially extending ports through which air may enter directly to the intake end of the air compressor housing, a valve means associated with an adapted to close the radially extending ports of said extension, a cowling disposed about said extension adapted to direct a flow of air to said radially extending ports and over and about said extension when said valve means is in its ports closing position, a plurality of air directing vanes forming a turbine nozzle ring at the discharge end of said cowling, and an air turbine rotor element secured to the rotor of said compressor and disposed in cooperating relation with said air directing vanes through which air may flow from said cowling to the intake end of the compressor when the ports of said extension are closed by said valve means,

whereby said impulse turbine nomle ring and rotor element will operate to throttle the flow of air to the intake of said compressor and return useful energy to the shaft of the gas turbine unit.

2. In a throttling arrangement for an open cycle combustion gas turbine unit of the type cmploying a directly connected axial flow turbocompressor, the combination of a compressor housing having stationary sets of blades arranged in axially spaced relation to form a multiplicity of air compressing stages, a rotor element mounted within said housing and having blades thereupon disposed in cooperating relation with the stationary sets of blades within said housing the output of said compressor being ducted to supply the total amount or air used by said gas turbine.

means for heating said air before entering said auxiliary air turbine unit having its rotor element secured to the rotor of said compressor and disposed within said cowling beyond said by-pass ports, whereby said auxiliary impulse turbine unit will operate to throttle the flow of air to the intake of said compressor and return useful energy to the shaft 01' the gas turbine unit.

3. In an air compressor throttling arrangement for open cycle gas turbine units of the character described, the combination of an axial flow compressor having an annular atmospheric air inlet at one end thereof the output of said compressor being ducted to supply the total amount of air used by said gas turbine, means for heating said air before entering said turbine, an air ilow directing cowling connected to the intake end of said compressor, a plurality of spaced radially extending nozzle forming partitions disposed at the discharge end of said cowling between which rality of partitions-so as to provide a multiplicity of radially spaced nozzle: therebetween, a plurality oi bellies within said cowllng for directing a. flow of air to each of the radially spaced sets of nozzles between said nozzle forming partitions, an impulse turbine rotor element having a plurality of radially extending blades with concentric partitions therebetween and forming a plurality of cooperating sets of buckets in cooperating relation with the plurality of nozzles between said nozzle forming blades, and a valve means assois in operation.

JAMES L. RAY.

REFERENCES CITED The following references are of record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 2,361,887 Traupel Oct. 31. 1944 2,371,889 Hermitte Mar. 20, 1945 2,405,282 Birmann Aug. 6. 1946 2,93,183 Forsyth July 1, 1947 2,438,357 Bloomberg Mar. 23. 1848 

